The goals of this investigation are to obtain a family of new fibroblastoid cell lines which are good producers of human interferon and to establish reproducible methodologies using these cells for the large scale production of human interferon (a minium target figure of 10 to the 8th power NIH reference units of interferon per disposable roller bottle). When sufficient interferon is generated from our procedures we shall use the interferon to ascertain whether human fibroblastoid interferon is more effective than human leukocyte interferon as an antitumor and cell growth inhibitory agent. The studies undertaken in this proposal now cover the following: 1. The enrichment in the copies of human chromosome 2 and 5 (involved in interferon production) by human x human cell hybridization as a means to obtain a class of extremely high interferon producing cells. 2. The creation of hybrid cells which will produce both human lymphoblastoid and fibroblastoid interferons and to use such hybrids as a means to stabilize human fibroblastoid interferon. 3. The evaluation of the potentials of fibroblastoid and of fibroblastlymphocyte hybrid interferon as an antitumor agent.